Cramer, D. W., Walker, A. M., & Schiff, I. (1979). Statistical methods in evaluating the outcome of infertility therapy. Fertility and Sterility, 32(1), 80-86. https://doi.org/10.1016/s0015-0282(16)44120-8
Cramer DW, Walker AM, Schiff I. Statistical methods in evaluating the outcome of infertility therapy. Fertil Steril. 1979;32(1):80-86. doi:10.1016/s0015-0282(16)44120-8
Cramer, Daniel W., et al. "Statistical methods in evaluating the outcome of infertility therapy." Fertility and Sterility, vol. 32, no. 1, 1979, pp. 80-86.
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Life tables can report infertility results by time to conception
A 1979 paper says life tables can report infertility results for similar patient groups. The Boston authors show the method with 10 made-up patients. They add a simple model of each couple's monthly chance of conceiving.
Study at a glance, methods paper of 10 made-up patients: Life tables can report infertility results by time to conception. Source: Cramer DW et al., 1979, PMID 456633.
Key Findings
In the authors' hypothetical 10-patient example, the cumulative probability of conception was 52% at the end of 1 year and 89% at the end of 2.
The same example had 7 conceptions over 108 person-months, an average monthly fecundability of 0.065, or a monthly chance of conception of 7% under treatment.
At a monthly fecundability of 0.20, approximately 75% of couples conceive within 6 months. At 0.05, only about 45% conceive within 1 year.
A monthly fecundability of 0.20 gives a mean waiting period of 5 months: 50% of couples conceive within approximately 3 months and 95% within 13 months.
After 24 months without conception, the authors judge it doubtful that a couple's true monthly fecundability is greater than 0.12.
Interpretation
This 1979 methods paper proposes life tables to report infertility results by time to conception, building on earlier infertility studies. The authors show the method with a hypothetical 10-patient example. They note that data from their own clinic were being prepared. The model assumes a steady monthly chance of conception, which the authors say holds unless follow-up runs past about 5 years. The findings support testing this life-table approach on real clinic data in future studies.
RRM Context
Restorative reproductive medicine looks for the cause. Grouping couples by similar diagnosis fits that goal. It gives results worth comparing. The authors call 1 year of infertility a fair definition of a fertility problem. The definition marks when to investigate, while leaving the cause open. Unexplained infertility means undiagnosed.
Our editorial summary of this paper, not the article's abstract.
Abstract
Lack of standardization in analytic methods for assigning infertility data is attributed to inadequate classification of fertility problems, and a lack of consistent methodology in evaluating outcome of infertility therapy. A classification scheme ideally should consider types of fertility problems as well as clinical assessment of its severity. Until an adequate classification system is developed, researchers are encouraged to describe fully the nature of infertility problem examined, and present results for homogenous groups of patients. The life-table method of analysis is a useful technique for assessing infertility statistics. The starting point of this method should depend on the group examined and may be either the date of 1st visit to the clinic or the date that therapy is instituted. Approximate date of conception should be the endpoint. A mathematical model of infertility predicated on the assumption that there is a constant monthly probability of conception of fecundability can be used to derive equations with potential for clinical application.
Research Methods › Measurement and Statistics › Statistical Methods · Clinical Guidelines and Standards › Diagnostic Criteria and Classification › Staging and Classification Systems
Daniel W. Cramer, Alexander M. Walker, Isaac Schiff
Dan Cramer, Danny Cramer, D Cramer, Alex Walker, A Walker, I Schiff
PMID 456633 456633 DOI 10.1016/s0015-0282(16)44120-8 10.1016/s0015-0282(16)44120-8 Cramer et al. 1979, Cramer 1979
Keywords
Actuarial Analysis, Evaluation Studies As Topic, Female, Humans, Infertility/therapy, Male, Models, Biological, Pregnancy, Statistics As Topic, Data Analysis, Demographic Analysis, Infertility, Life Table Method, Mathematical Model, Reproduction, Research Methodology, Surveys
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